Conversion of heavy hydrocarbonaceous materials



R. w. SAGE 2,733,192

CONVERSION OF HEAVY HYDROCARBONACEOUS MATERIALS Filed July 3l, 1951 Rif/10rd rsge {SQA/amber United States Patent C) CONVERSION F) HEAVY HYDROCARBONA- CEUS- MATERIALS Richard W. Sageh`anwood, N. 1..assignor to Esso Research and Engineering CompanygA a corporation of Delawarel Application July. 31, 1951-, seria1No. 239,491

2 claims. (ci. 19a-so) The .present invention relatesto a method :of treating hydrocarbons. Morey specifically, the invention pertains to. an improved process of reducing the viscosity of heavy hydrocarbonaceous residues of the type. of topped or reduced crude, asphalt, pitch, or similar materials by a thermal treatment suitable to produce vmotor fuel range hydrocarbons, gas oils and fuel oils of improvedquality. In yits broadest aspect, the invention provides for subjecting rheavy residues of the type specified to a deoxygenation treatment lfollowed by a viscosity-reducing lor visbreaking treatment at high temperatures and elevated pressures to p roduce gasoline, gas oils and. low sediment fuel oil.

In retningcrudey oil the first vstep is normallya simple distillation or topping to produce distillatel fractions and a heavy residue. In order to obtain,- maximum yields of high quality motorv fuels, andmiddle distillate fractionssuitable as heating oils, the crude oil fractions boiling above about 650F. must be broken down into lower molecular weight compounds boilingin therange of 0F. to 650F. It is very desirable economically to produce` fromthe materialboiling higher than heating oil a maximum amount of heavy gasoil by distillation, light hydrocarbon precipitation, etc., this gas oil being processed by either thermal or catalytic. cracking toachieve the maximum yields of high value motor fuels and heating oils discussed above. The residue (reduced crude) from the preparation of the heavy gas oil is disposedof as heavy (residual)` fuel oil, usually after liuxing with a less` viscous oil to a more usable viscosity. In.. order to, obtain a maximum of highvalue products from the heavy residue and to minimize the amount ofr heavy fuel produced (and also, to minimize the amount of ux oil required for viscosity reduction) theresidue itselfis also subjected to a .thermal cracking operation asdescribed below.

The thermal cracking ofl reduced crudes is known as. visbreaking and yields gasoline,.heating oil andl gas oil as well as a reduced. amount of residual materialfor a givenviscosity. Visbreaking involves a treatment ofreduced` crude o r theI like at temperatures of,` about. 780 950.F.= and pressures ofabout 10011500 p. s. i. g. at feed. rates. of 2-75 volumesn perl hour of yoil, atA 60F. per crackingr volume above 750 F. to4 produce by amild type offthermal cracking about5-40 vol. per centof gas oil, about 5-25 vol. per cent of gasoline and about 85-60- vol. per cent of heavy fuel oil. Specific conditions within; the ranges specified depend on the type andy boiling range of the visbreaker feed. The, gas oil so formed represents a feedstock suitable for the production of additional amounts of high quality gasoline by catalytic cracking or, after suitable finishing, anY acceptable distillate fuel.A Of the products'formed lin visbreaking, the gasoline ands gas oil have the highest and thefuel oil the lowest values.

Quite generally, therefore, it isv desirable` in visbreakingto reduce fuel oil yields'in favor of higher yields of gasoline and gas oils. However, procedures suitable forv this purpose, for example operating atan increased thermalcrackingseverity, affect .detrimentally the, quality 2,733,192 .Patented Jan. .3.1, 1956 vICC ofthe fuel .oil. v Itis;` particularly. difcult to, produce :a fuelv oil of vsatisfactory sedimentation characterisics along. with maximum .yieldsof gasoline, and'gasoils. Any process -by which,thequality ofthe fuel oil portion of the visbreaker productmaybeimproved while increasing theA yields. of other productsis,therefore, of greatest in. terest. The present invention provides a process yofV this type.

It is, therefore.the principal objectV of the invention to. provide means for .producinga fuel oil, o f improved quality by visbreakin'g, heavy hydrocarbonaceous residues. Other objects and advantages will appear from the sub-` sequent dc'escriptionv ofthe invention wherein ,reference will-befmade--to` the;A accompanying drawing,fthe single figure ofy Vwhich is a semi-diagrammaticall illustrationk of a system-suitable to-carry out a preferred embodiment of the-invention.v

In accordance with-the presentv invention, visbreaker feed stocks: such lasfA reduced crude-orsimilar residues of the-type specified above are subjected to a deoxygenation treatment. immediately, prior to being passed to the visbreaker unit. The deoxygenationtreatment should. be carried'out in'such a manuel-fasy topermit the substantially complete removatl off the free; oxygen contained in the visbreaker; feedz;v Stripping of thel feed with steam or otlrierf gases Y suchl as nitrogenV or `inert Y gas consisting predominantlyfof; nitrogen and/ or carbonl dioxide at elevated temperatures-,off aboutf220 to 7.5,0F. and atmospheric onslightlyelevated pressures issuitablefor this purpose. Lower pressures than atmospheric may be employed-,if

` desired.

It has been found that ,thesediment-forming tendencies andasphaltenecontent of visbreaker tars increase appreciably upon contact, offthese tarsiwith free oXygCn.. The expr-:rimentsA reported below bear out this fact.

Av reduced v'crude (I.`BQ. P.A l,050."F.1) was visbroken at about 930F. and 3'50p. s. i.y g. for about 4`minutes above 751.0F.` rll'ie product was ashed to atmospheric pressure andheavy tar (about 600 F. I.` B. P.) was separated from the gasoline and gasoils: The tar-was iiuxed with gas oil to'a Saybolt Furol';viscosity of 175 seconds at l22Fj The; blend was*A then l'testedl for sediment and asphaltene'Y contente-priori to4 and aftertreatmentwith oxygen-.-v

Sedimer'lt`- was determined byy filtration after tluxing, sediment` beingA reported 'as weight percent of "uxed tar; Fuel oil blends-havingasedimentin excess of 0.3' wt. percent-are considered unsatisfactory. Asphaltenes were determinedby precipitationwitha,light-petroleum naphtha andi measured-as weight-1 per e cent` of insoluble-matter; The oxygen treatment-consisted` inf bubbling oxygen through the blend for one hour at 2`12FF.' The results.

of thesetests-aresummarized below.

Condition-ot Fluxed `Tar dfcrt Prior tofTreatment k .26 Y 12.8 After On-Treatment. 1 1. 8 14. 5

y It-.will be;A noted that: both4 sediment and asphaltene content ywere, materially increasedby theoxygen treatment,v Increases. of. -this.order seriously limit the value treatment, with oxygen;l Thesel tests prove the particular sensitivity of ,visbreak,er tar` to the influence of` free oxygen..

Visbreaker feed stocks like all other petroleum prodi ucts contain free oxygen pickedup in varying amounts from the air particularly during storage for an appreciable length of time. This oxygen causes, in the course of the visbreaking treatment, the formation of sediment and asphaltenes in the manner demonstrated by the above experiments. The severe conditions of temperature and pressure employed in the visbreaking operation, combined with the ne and uniform distribution of the oxygen in the feed strongly favor these undesirable side reactions.

The present invention eliminates these side reactions by removing the oxygen from the visbreaker feed. In this manner, the severity of the visbreakng treatment may be substantially increased `so as to increase the yields of gasoline and gas oils without the simultaneous deterioration in the quality of the fuel oil product which has been previously experienced. The beneficial effects of the invention may be further enhanced by excluding air or free oxygen from visbreaker tar particularly at temperatures substantially above 100 F.

Having set forth its objects and general nature, the invention will be best understood from the more detailed description hereinafter read with reference to the drawing. The system illustrated in the drawing essentially comprises a deoxygenation tower 17, a visbreaking coil 35 and a separator tower 40. The functions and coaction of these elements will be presently described in connection with the treatment of a mixed feed of different renery residues. It should be understood, however, that the system may be employed in an analogous manner for the visbreaking of other hydrocarbonaceous residues.

In operation, refinery residues from various sources may be fed to the visbreaking unit. For example, a residue from the atmospheric distillation of crude oil may be withdrawn from tankage and supplied via line 1. This material which may have a boiling range of about 500 to 1500I F. or higher may amount to about 5 to 50% of the total feed. Its oxygen content may be relatively high, amounting to, say, about 0.05 to 0.5 standard volumes of gaseous oxygen per liquid volume of residue chiefly as a result of long time storage. If desired, this portion of the feed may be preheated in a suitable heat exchanger 3 to about 500 to 700 F.

A second feed portion may be supplied through line 5 in the form of vacuum still bottoms. This material which boils above about 1050 F. usually has a relatively low oxygen content and may make up about 30 to 80% F of the total feed. It is preferably supplied at the temperature of the vacuum still of, say, about 60G-800 F. The remainder of the feed may be visbreaker products, extraneous gas oils etc., supplied to the system via line 7 at about 400-600 F.

The combined feed which may have a temperature of about S50-700 F. is passed through line 9 preferably to the convection section of coil furnace 11 to be heated in coil 13 to temperatures up to 800 F. The preheated feed is then further treated as follows.

Coil 13 discharges into line 15 which leads to the top of deoxygenation tower 17. The feed enters tower 17 through suitable distributing means such as spray nozzles 19, preferably at atmospheric or slightly elevated pressure of, say, 0-30 p. s. i. g. and predominantly in the liquid state. The temperature is maintained within the range of about 220 to 750 F. Tower 17 may be a bubble plate, disc-and-doughnut, or packedV tower of :t design conventional in the art of distillation and countercurrent liquid-gas contacting. A tower provided with disc-and-doughnut baies 21 is shown in the drawgSteam preheated to about 50G-800 F. is injected from line 23 through nozzles 25 into the bottom of tower 17. About 0.5-2.0 lbs. of steam per gallon of oil tion.

feed is normally sufficient for the purposes of the inven- Free oxygen is stripped olf the oil feed by the countercurrently owing steam. A mixture of steam and oxygen is withdrawn overhead from tower 17 to be vented or passed via line 27 to a condenser for recovery of any minor amounts of heating oil and lighter products distilled off during stripping. Substantially complete deoxygenation of all practical visbreaker feed stocks may be accomplished within stripping times of about 10 to 60 seconds at the conditions specified.

When other stripping media such as nitrogen or mixtures of nitrogen and carbon dioxide are used in place of steam, stripping rates may be slightly lower and longer times required. The stripping agent shouldV be completely devoid of free oxygen.

The oil feed now substantially free of oxygen, is withdrawn from tower 17 through line29 and passed by means of pump 31 to preheating coil 33 and visbreaker coil arranged, respectively, in the convection and radiant sections of furnace 11. The oil may enter coil section 33 at a temperature of about 650-750 F. and a pressure of about 10D-1500 p. s. i. g., preferably about 300 to 400 p. s. i. g. The temperature of the oil in section 33 may reach about 70D-850 F. Heating is continued in section 35 to a temperature of, say, about 850-950 F. Coil dimensions and oil feed rates are preferably so correlated that the oil residence time at visbreaking temperatures exceeding 750 F. will be about 0.8-30 minutes, corre spending to an oil throughput of about 75-2 volumes of liquid oil per volume of visbreaking coil per hour (v./v./hr.).

The visbroken product is withdrawn at visbreaking pressure and a temperature of about S-950 F. in mixed vapor-liquid phase via line 37. The product is flashed by means of pressure release valve 39 into a lower portion of the baflled section of a separator tower 40 at a temperature of about 800-900" F. and a pressure of about 20-100 p. s. i. g. Stripping steam may be admitted to the tower 40 via line 42 at a point below the feed point of line 37 to aid in the removal of distillateproducts including gasoline and gas oil which leave tower 40 overhead through line 44 to be further worked up in conventional fractionation and treating equipment, not shown.

Heavy visbreaker tar of a boiling range suitable for inclusion in heavy fuel oil is collected in tar pot 46 and may be handled therein as follows. Product tar may be withdrawn via line 48 and passed to storage at a rate controlled by valve 50 operated by conventional level control means 52, such as a conventional ball oat or differential pressure controller. The tar level in tar pot 46 is preferably so adjusted that a substantially constant tar hold up .and a relatively short tar residence time are provided at the residuum feed rates here specified.

The system of the drawing permitsof various modifications. If desired, the tar pot may be maintained at a desirably low temperature of about 400-650 by continuously circulating tar from the tar pot through a cooler and baclcto the tar pot. Another stream of relatively cool 'product tar may be returned to line 37 to quench the visbreaker product vto any desired temperature between about 450 and 800 F. Other modifications will appear to those skilled in the art.

The above description and exemplary operations have served to illustrate specific embodiments of the invention. It will be understood that the invention embraces such other variations and modifications as come within the spirit and scope thereof.

What is claimed is:

l. The process of `converting heavy hydrocarbon oils into distillate oils and tar, which comprises distilling from said oils the' constituents boiling below 650 F. to produce residual oils, stripping said residual oils so produced in a stripping zone with steam at a temperature of about 220 tov 750 F'. with about 0.5-2.0 lbs. of steam per gallon of residual oil so as to remove free oxygen substantially completely from said residual oils, recovering overhead from said stripping zone steam, oxygen and a minor amount of oils distilled during the stripping, immediately thereafter subjecting said oxygen-free residual oils to a vis-breaking treatment at relatively severe conditions including temperatures of about 850 to 950 F., pressures of about 30D-400 p. s. i. g. and oil throughputs of about 2-75 v./v./hr. adapted to produce a vis-broken material relatively rich in distillate fractions, and Hash-separating said material at a substantially lower pressure into distillate fractions and heavy tar suitable as a residual fuel oil.

2. A method of inhibiting sedimentation and asphaltene formation during vis-breaking of heavy hydrocarbonaceous residues containing free oxygen which comprises completely deoxygenating said residues by steam stripping in a deoxygenation zone using steam in an amount in the range of 0.5 to 2.0 lbs. per gallon of said residues for a time in the range of 10 to 60 seconds, recovering References Cited in the le of this patent UNITED STATES PATENTS 1,776,598 Rather et al. Sept. 23, 1930 2,141,623 Downey Dec. 27, 1938 2,196,878 Stover Apr. 9, 1940 2,249,884 Carney July 22, 1941 2,271,095 Roberts Jan. 27, 1942 2,349,428 Hemminger May 23, 1944 

1. THE PROCESS OF CONVERTING HEAVY HYDROCARBON OILS INTO DISTILLATE OILS AND TAR, WHICH COMPRISES DISTILLING FROM SAID OILS THE CONSTITUENTS BOILING BELOW 650* F. TO PRODUCE RESIDUAL OILS, STRIPPING SAID RESIDUAL OILS SO PRODUCED IN A STRIPPING ZONE WITH STREAM AT A TEMPERATURE OF ABOUT 220* TO 750* F. WITH ABOUT 0.5-2.0 LBS. OF STREAM PER GALLON OF RESIDUAL OIL SO AS TO REMOVE FREE OXYGEN SUBSTANTIALLY COMPLETELY FROM SAID RESIDUAL OILS, RECOVERING OVERHEAD FROM SAID STRIPPING ZONE STREAM, OXYGEN AND A MINOR AMOUNT OF OILS DISTILLED DURING THE STRIPPING, IMMEDIATELY 